Receiving screens for optical images for advertising purposes are already known, which are made of fixed or mobile surfaces placed inside cyindrical or spherical volumes (see particularly French Patent 2,116,789).
There also exist screens placed along a diametrical plane inside a sphere. These screens, which are translucent screens and of a circular shape, rotate about themselves and receive an image from a projector, which image, since the screens will rotate, starts with a determined size, develops, then shrinks and finally disappears (see French patent 2,266,249).
A rotating screen of the type just described is also known, but with a spherical volume formed of a transparent or translucent front half-sphere and a rear half-sphere which is opaque except in the central axis for permitting light rays forming the image to enter the sphere and reach the rotating screen (see French patent 2,448,734).
All these known apparatus have disadvantages since the image formed on the screen is more or less well suitably seen by the spectators. Actually, in premises which are lighted by artificial light or day light, the image is more or less visible, and moreover, when the screen rotates, the image is deformed with sometimes good results but also sometimes particularly bad results. Moreover, the rotating screen requires installation of a motor unit which is rather fragile and increases the cost of the apparatus.